kW and kWh are very different metrics. It's the same as confusing gallons with horsepower. Think of kW = horsepower, kWh = gallons.

If one charges at 1 kW (or 1000 watts) for 6 hours, 6 kWh came out of the wall. If it's at 6 kW for 1 hour, it's also 6 kWh. If it's 1 watt for 6000 hours, it's also 6 kWh.

One pays for electricity at home in cents per kWh. There are a few utilities w/residential plans where they not only bill per kWh but also have demand charges, but that's rare and complicates calculations. (Demand charges aren't unusual on many commercial plans.)

Leaf has ~21 kWh usable battery but since charging isn't 100% efficient, it takes more than 21 kWh out of the wall to fully charge a dead Leaf. viewtopic.php?p=155305#p155305 has some figures, but it was before the '13+ Leaf w/optional 6 kW on-board charger.